The invention relates to a retention member for securing a unit, in particular a pump, to a motor vehicle. The retention member has an annular damping element whose inner region is provided for receiving the unit. At the outer side, the damping element has a block-like securing element whose upper side which is directed radially away from the center of the damping element is provided as an interface to the motor vehicle, there being arranged in the securing element, below the upper side, a substantially plate-like insertion member which is configured to locally reinforce the damping element.
Retention members of this type are already commercially available.
In the construction and configuration of system components, such as, for example, a cooling circulation pump for a motor vehicle, the dynamic loads which are to be anticipated during operation of the motor vehicle, in particular the components of the system components, such as printed circuit boards and pin connections, are a challenge for developers with respect to durability. Often the high specification requirements, the narrow structural spaces and the cost pressures lead to undersizing of critical components, which may lead to failure of an individual component and consequently also the unit.
An example of this in this instance involves requirements for the vibration-resistance of the unit when fitted to an internal combustion engine of the motor vehicle. The resulting dynamic loads of the products often far exceed the permissible load-resistance. Missing or inadequate material damping systems often bring about, in the case of vibration loads, critical resonance frequencies with the excitation being exceeded by up to 20 times and consequently significantly limit the desired service-life of the product. In this instance, the transmission intensity of the oscillation energy of the oscillation exciter, that is to say, the internal combustion engine, on the product secured thereto, as far as the individual components, is highly dependent on the connection type of the components and the material dampings thereof. A rigid retention of the pump on the engine means undamped transmission of the excitation energy to the pump and consequently an excessively high loading of the pump, or the individual components thereof.
The service-life of a product is inversely proportional to its loads, the stresses being able to be decisively minimized by means of a damping. For a resilient retention system, highly-damping elastomer buffers are suitable, for example, comprising EPDM (ethylene propylene diene monomer rubber) which absorb the oscillation energy and convert it into internal friction; heat which the elastomer material discharges outwards is produced.
In known retention members, the damping element is typically mounted as an annular retention member/decoupling element between the unit and the oscillation exciter, cf., for example, DE 10 2009 029 067 A1. This is an efficient solution with respect to damping but, as a result of the low level of rigidity of the elastomer retention member, brings about undesirably great occurrences of deflection of the unit (in particular in the low frequency range) and can lead to a collision with adjacent components. Furthermore, an excessively resilient retention member, for example, as a result of the assembly forces which occur when the connector is mounted on the pump, can lead to occurrences of expansion or displacement of the pump, which make subsequent assembly of the pump more difficult. In order to eliminate the danger of the unit being shaken loose from the elastomer retention member, an additional annular retention sheet is often also required.
During the configuration of an elastomer retention member, therefore, it should be ensured that, at one side, a minimum damping for decoupling the pump has to be present and, at the other side, a maximum deflection (dependent on the structural space and assembly conditions) must not be exceeded. In principle, this can be achieved, for example, by means of a suitable Shore hardness of the elastomer mixture or by means of an insertion member for reinforcing the elastomer retention member, preferably of steel or thermosetting material.